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Race converterHalf marathon to marathon time converter
Your marathon prediction is roughly 2.07× your half marathon time: a 1:50:00 points to about 3:47:50, if you train for the longer race. The half marathon is the race most runners use to set a marathon goal, and the old rule of “double it and add ten minutes” is a reasonable first check.
| Distance | Predicted time | Pace |
|---|---|---|
| 5 km | 23:55 | 4:47/km |
| 10 km | 49:37 | 4:58/km |
| 15 km | 1:16:25 | 5:06/km |
| Half marathon | 1:50:00 | 5:13/km |
| Marathon | 3:47:50 | 5:24/km |
| Two Oceans 56 km * | 5:23:38 | 5:47/km |
| Comrades (about 90 km) * | 9:42:51 | 6:29/km |
Flat course, good conditions, properly trained for the distance. * Past the marathon, times follow how real Two Oceans and Comrades fields finish (about 1.42× and 2.56× a marathon), not the pure fitness model.
The chart
| half marathon | Marathon (VDOT) | Riegel | Pace |
|---|---|---|---|
| 1:25:00 | 2:57:25 | 2:57:13 | 4:12/km |
| 1:30:00 | 3:07:35 | 3:07:39 | 4:27/km |
| 1:35:00 | 3:17:43 | 3:18:04 | 4:41/km |
| 1:40:00 | 3:27:47 | 3:28:30 | 4:55/km |
| 1:45:00 | 3:37:50 | 3:38:55 | 5:10/km |
| 1:50:00 | 3:47:50 | 3:49:21 | 5:24/km |
| 1:55:00 | 3:57:48 | 3:59:46 | 5:38/km |
| 2:00:00 | 4:07:45 | 4:10:12 | 5:52/km |
| 2:10:00 | 4:27:33 | 4:31:03 | 6:20/km |
| 2:20:00 | 4:47:17 | 4:51:54 | 6:49/km |
| 2:30:00 | 5:06:58 | 5:12:45 | 7:16/km |
Two formulas, one answer
The VDOT column is Jack Daniels’ model, the same one that sets every Race Shape plan. The Riegel column is Pete Riegel’s 1977 formula, T₂ = T₁ × (D₂/D₁)^1.06, which most online calculators use. For a 1:50:00 half marathon they give 3:47:50 and 3:49:21. When two independent models agree to within a few minutes, the estimate is about as good as a formula gets.
When the prediction is wrong
The model predicts a little more than double — roughly 2.1× — because pace falls as distance rises. Runners with high mileage often beat it; first-time marathoners usually do not.
At altitude, add the correction on top: a race at Johannesburg’s height is about 8% slower for the same effort — see the altitude pace calculator.
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Common questions
How do I convert a half marathon time to a marathon time?
Multiply by about 2.07, or use the chart: a 1:50:00 points to about 3:47:50.
What marathon can I run off a 1:30:00 half marathon?
About 3:07:35 by Daniels’ model, 3:07:39 by Riegel’s, if you train for the marathon.
Which is more accurate, VDOT or Riegel?
They agree closely over these distances. VDOT is slightly more conservative for slower runners; neither knows how much long-run training you have done, which matters more than the formula.
Why did I run slower than my predicted marathon?
The model predicts a little more than double — roughly 2.1× — because pace falls as distance rises. Runners with high mileage often beat it; first-time marathoners usually do not.